There is a liquid discharge apparatus equipped with a recording head having a liquid droplet discharge head which discharges droplets of a recording liquid, which is used in various image forming apparatuses such as a printer, a facsimile machine, a copy machine, a combination machine, etc.
In such an image forming apparatus, it is very important to maintain and recover a performance of a recording head that discharges a recording liquid. A maintenance and recovery device performs such a maintenance and recovery of a recording head. Generally, such a maintenance and recovery device comprises a moisture retention cap, a suction cap, a wiper blade and a blank discharge receiver for receiving liquid droplets of a blank or blank discharge that does not contribute to image formation.
As a cap member in such a maintenance and recovery device, there is known, as disclosed in Japanese Patent Publication No. 3106783, a cap that has a first inclined surface, which inclines toward an ink discharge port with a gentle slope, and a second inclined surface, which inclines toward the ink discharge port with a steep slope so as to eliminate ink remaining in the vicinity of the ink discharge port.
Additionally, there is known, as disclosed in Japanese Laid-Open Patent Application No. 2001-71514, a cap that has a space part of a tapered shape, which continuously narrows toward an ink discharge port and provided with an ink retaining means in a passage that connects an ink suction port to a negative pressure generating means so as to discharge ink inside the space part to maintain moisture retention by ink in the passage.
Further, there is known, as disclosed in Japanese Laid-Open Patent Application No. 6-23891, a cap that facilitates suction of ink by improving water repellency of an inner surface of the cap.
Additionally, there is known, as disclosed in Japanese Laid-Open Patent Application No. 2003-1839, a cap that improves airtightness by being provided with a resilient seal member covering a nozzle plane and a rigid member forming a sealing part, these members being formed by materials having water repellency of a contact angle equal to or greater than 90° with respect to ink.
As a colorant of ink used for an inkjet recording apparatus as an image forming apparatus, dye ink was a main stream at the beginning in viewpoint of a merit of its coloring nature and reliability. However, in recent years, pigment ink using a pigment such as a carbon black tends to be used so as to provide light resistance and water resistance to a recorded image. Moreover, there is a tendency to set a high viscosity to ink for the purpose of increasing a degree of freedom of ink prescription and preventing blur of ink after an ink droplet landed a regular paper.
Such a high viscosity pigment ink changes in its viscosity due to a change in temperature. For example, ink having a viscosity of 8 cps at an ambient temperature of 22° C. may have a viscosity of more than 15 cps at 10° C. and a viscosity of about 5 cps at 32° C. It was found according to experiments by the inventors that, when such ink is suctioned by a conventional cap member, it is difficult to discharge the ink stably.
That is, it was found that the cap member, which is disclosed in Japanese Patent Publication No. 3106783, having a first inclined surface, which inclines toward an ink discharge port with a gentle slope, and a second inclined surface, which inclines toward the ink discharge port with a steep slope, can reduce a residual amount of ink, but, discharge of the ink is not sufficient when pigment ink, especially ink having a viscosity of equal to or higher than 5 cps, is used.
It was also found that the cap member disclosed in Japanese Laid-Open Patent Application No. 2001-71514 cannot sufficiently discharge ink when pigment ink, especially ink having a viscosity of equal to or higher than 5 cps, is used.
Moreover, it was found that the cap member disclosed in Japanese Laid-Open Patent Application No. 6-23891 can facilitate suction of ink by improving water repellency of an inner surface of the cap, but discharge of ink is not sufficient when ink containing pigment, especially ink having a viscosity of 5 cps and a surface tension equal to or smaller than 40 dyne/cm is used since wetability of the ink is extremely high even the water repellent treatment is applied.
Moreover, it was found that the cap member disclosed in Japanese Laid-Open Patent Application No. 2003-1839, which is provided with a resilient seal member covering a nozzle plane and a rigid member forming a sealing part that are formed by materials having water repellency of a contact angle equal to or greater than 90°, cannot be used practically when ink having a viscosity of 5 cps and a surface tension equal to or smaller than 40 dyne/cm is used since it is difficult to apply a water repellent treatment to set a contact angle with respect to the ink to be equal to or grater than 60 degrees.